The long-term goal of our studies is to understand the molecular and genetic elements that underlie the process of aging and determine longevity. The aim of this proposal is to understand how mutations in a single gene, Indy, result in a dramatic increase in life span in Drosophila melanogaster without a concomitant loss of reproduction, physical activity or metabolic rate. In particular we will seek to determine where and when Indy mutations act to extend life span. The function of the INDY protein as a tranporter of Krebs cycle intermediates and its preliminary localization to regions of the fly important in uptake, utilization and storage of nutrients, indicate that reductions in the level of INDY protein alters the metabolic state of the fly in a way that favors life span extension. INDY's similarity in sequence, function, and tissue expression to mammalian and human dicarboxylate transporters suggests that knowledge of how Indy mutations extend life span in flies may be useful for the development of therapeutic interventions for extending healthy life in humans. We will first examine the tissues and times during life INDY expression is altered in the long-lived Indy mutant animals. Using molecular genetic approaches we will restore Indy function to directly determine where and when Indy mutations act to extend life span. Finally we will determine which of the several possible human Indy-like genes can functionally rescue the Indy mutation. A more complete understanding of how mutations in Indy lead to life span extension should yield valuable insights into general mechanisms of life span extension relevant to a variety of organisms including humans.